Dan Smith - the ex-Portsmouth player who spent the second half of 2018-19 on loan in Ireland with Cork City - notched the only goal of the game with a neat low finish shortly before the interval.
Jimmy Muitt went close early on for Bognor before Kareem Haitham was denied by Pompey loanee Petar Durin at the other end.
The Rocks stopper was called into action again, this time as he tipped wide from forward Lloyd Rowlatt, and Jamie Horncastle nodded off a post from the resultant corner.
The pendulum swung back Bognor’s way as three openings came and went in as many minutes, all from the boot of that man Muitt.
He smashed over the bar from a Stuart Green cut-back, Ant Ender came to his side’s rescue with a smart stop, and the Bognor number 10 then sliced an opportunity wide from the edge of the box.
The dust had barely settled on that glut of chances before the breakthrough arrived five minutes before the break.
Doug Tuck advanced through midfield and found Smith, whom dropped the shoulder and placed the ball under the reach of Ender to send his side in ahead at the interval.
Chi sub Rory Biggs went close from distance and Scott Jones fizzed over the bar, but the best chance of the second-half fell to Bognor in the closing stages. Muitt linked up with Dan Simmons who seemed poised to score but Ender stretched every sinew to tip his diving header over the bar and keep his team in the contest.
A combination of Bognor’s good game management and a flurry of changes from both sides saw the tie meander to a conclusion, but in the end it is the Sussex Senior Challenge Cup winners that begin the 2019-20 season with silverware already secured in the trophy cabinet!